Applying mulch to your garden and landscape provides a number of benefits, including reduced erosion and water loss, improved soil nutrition and a more balanced soil temperature. Different kinds of mulch provide these benefits at different levels.
Mulch is anything used to cover the landscape bed. Mulch can be shredded wood, pine needles, straw, sawdust, gravel, or river rock. Here in Nebraska and Iowa, hardwood mulch is most commonly used and readily available. Hardwood mulch comes in natural brown and color enhanced chocolate which is dyed a dark brown chocolate color. The chocolate is most popular and is approximately $10 per cubic yard more expensive than natural hardwood. River rock is also a popular choice depending on your application and your budget.
At Jensen Gardens, we offer two types of mulch: natural hardwood mulch in medium brown, and color-enhanced hardwood mulch in dark chocolate.
Tip to find out how much mulch you need:
(Length of bed) x (Width of bed) x (Depth in feet (3” is 0.25ft)) / 27 = Cubic Yards.
Wood mulch and other organic mulches insulate the soil and roots of plants keeping them cooler in the summer and insulated and protected in the winter. River rock absorbs heat and holds onto heat increasing the soil temperature in the summer and offers very little insulation in the winter. If you are in full sun consider using wood or other organic mulch around your plants.
Cost and Durability
River rock is considerably more expensive than organic mulches such as shredded bark, wood chips or compost and comes in at about three to six times the cost of organic mulches. But because river rocks don’t decompose they don’t need to be replaced or top dressed each season. River rock requires a weed barrier fabric to be laid underneath it to prevent weeds and also to prevent the rock from sinking into the soil. The average river rock bed lasts 10-15 years. Weed seeds and silt blow in and leaves and twigs fall from trees and bushes and decay. All this builds up over time and eventually requires that the rock beds be renovated.
Most organic mulches need a fresh top dressing of 1-2 inches applied every 1-2 seasons. River rock and similar inorganic mulches do not need to be replaced, but they may require periodic washing/blowing or the addition of a new upper layer of stones. This type of mulch is heavy and can be difficult to move or adjust after it is put into place. Both wood mulch and river rock will require periodic weeding.
Mulches made from bark, wood or other organic materials slowly compost into the soil over time, providing a great source of organic matter and a renewable source of nutrients for plants. This is why we do not recommend a weed barrier fabric underneath mulch. The weed barrier will inhibit the bottom layer of mulch from composting into the soil. There are many benefits to this composting layer: increased soil porosity, increased beneficial bacteria in the soil that help with plant root growth, increased water absorption, increased soil aeration. River rocks do not provide any additional nutrition. Plants grown under river rock or other inorganic mulch materials may need supplemental feeding and supplemental watering.
Mulches can be used to decrease water loss. In areas where conservation is a significant concern, wood mulches perform much better than river rock. In a study performed by the University of California, small stones held only 0.09 inches of water per 1 foot of mulch, compared to between 1 and 3.64 inches per 1 foot for bark, compost, yard waste and other organic materials. For water conservation we recommend wood or other organic mulches over rock.
In high erosion areas and waterways, we recommend installing a non-woven geotextile filter fabric installed with a layer of large river rock to slow down the water, hold the soil and prevent erosion. Wood and organic mulches will wash out from these areas.
Tip: When installing both weed barrier fabric and filter fabric make sure you overlap the joints 6” and secure the fabric to the ground using 6” steel fabric staples every 1-4 ft as needed to securely hold the fabric in place.
Both wood mulch and river rock provide weed control. River rock must be combined with landscape fabric. River rock can still be penetrated by aggressive weeds, requiring occasional hand weeding. Wood mulches provide slightly reduced weed deterrent properties for the first few years. Both river rock and wood mulch are far better than bare soil for weed control. After 4-6 years, the river rock beds silt in and build up organic matter to a point where they will have occasional weeds sprout on top of the weed barrier fabric, making the weed control of river rock vs. the weed control of wood mulch the same.
In conclusion, both river rock and wood mulch have their benefits and drawbacks.
Wood mulch is your best choice for:
- Low cost mulch cover
- Densely planted plants
- Beds in full sun
- Beds where water conservation is important
River Rock is the best choice for:
- Beds requiring water erosion prevention
- Beds where river rock is the desired look
- Beds around pools
Feel free to mix and match mulches for different areas. We utilize hardwood mulch for most of our landscape planting beds and incorporate river rock by creating dry stream beds for downspouts and waterways. Regardless of your budget and preference, know that any kind of mulch is an improvement over bare soil.